Field of the Invention
The invention relates to the field of emission reduction and resource utilization of carbon dioxide from flue gas of a power plant boiler, and more particularly to a method and an apparatus for collecting carbon dioxide from flue gas.
Description of the Related Art
The chemical absorption method is widely applied in industries for capturing CO2, and the principle of the chemical absorption method is as follows: CO2 in the flue gas reacts with a chemical solvent and is absorbed thereby. A rich solution of the chemical solvent is acquired after absorbing CO2 to an equilibrium state; then the rich solution is introduced into a regeneration tower, heated and decomposed for releasing CO2 gas and being transformed into a barren solution. Thereafter, the barren solution is recycled to absorb CO2 from the flue gas. Thus, by circulating an absorbent solution between an absorption tower and the regeneration tower, CO2 in the flue gas is captured, separated, and purified. Currently, the chemical absorption method using an amino alcohol solution to absorb CO2 is the most widely applied method, which specifically includes: an MEA (monoethanolamine) method, an MDEA, and a mixed organic amines method. In practice, it has been proved that, although the chemical absorption method using the amino alcohol solution has the characteristics of fast absorption speed, strong absorption ability, it still has the following defects when utilized in treating flue gas from power plant: 1) the oxidative degradation of the amino alcohol affects a long term and stable operation of the apparatus, and the solution consumption is large; 2) the apparatus is seriously corroded; and 3) MEA generally has a concentration of less than 20%, and thus the CO2 absorption rate is low, but the energy consumption in regeneration is high. All these reasons result in the high cost of the method for collecting carbon dioxide by using amino alcohol.